What you describe has sometimes been a situation of low battery charge. If you let the car sit for long or don't drive very far each day (my total rd trip commute is 6 miles and not enough) there is enough parasitic drain that never gets caught up without a good 20 minute drive or so. I have a good weather car and the X3. When I take one out the other sits on a battery tender to ensure full charge even though I may not have driven the sitting car for 2-3 weeks. I used to get these two warning lights and since I changed to the battery tender process I haven't seen them in more than a year.
Oh, and I have not replaced the original battery either.
'00 MRoadster, '00 528 now in other hands, '07X3si, '14 535d XDrive